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Number of results: 113
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Abstract

The paper presents an innovative method of creating the layered castings. The innovation relies on application the 3D printing insert obtaining in SLM (selective laser melting) method. This type of scaffold insert made from pure Ti powder, was placed into mould cavity directly before pouring by grey cast iron. In result of used method was obtained grey cast iron casting with surface layer reinforced by titanium carbides. In range of studies were carried out metallographic researches using light microscope and scanning electron microscope, microhardness measurements and abrasive wear resistance. On the basis of obtaining results was stated that there is a possibility of reinforcing surface layer of the grey cast iron casting by using 3D printing scaffold insert in the method of mould cavity preparation. Moreover there was a local increase in hardness and abrasive wear resistance in spite of the precipitation of titanium carbides in surface layer of grey cast iron. While the usable properties of composite surface layer obtained in result of use of the method presented in the paper, strongly depend of dimensions of scaffold insert, mainly parameters Re and Ri.
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Abstract

In this paper results of microsegregation in the newly developed nodular cast iron with carbides are presented. To investigate the pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen. The distribution of linear elements on the eutectic cell radius was examined. To investigate the microsegregation pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen. The linear distribution of elements on the eutectic cell radius was examined. Testing of the chemical composition of cast iron metal matrix components, including carbides were carried out. The change of graphitizing and anti-graphitizing element concentrations within eutectic cell was determined. It was found, that in cast iron containing Mo carbides crystallizing after austenite + graphite eutectic are Si enriched.
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Abstract

The contribution summarises the results of oxygen activity determinations, which were measured and registered continuously in castings from cast irons with various types of graphite. The results were used to find the relationship between two variables: natural logarithm of oxygen activities and reverse value of thermodynamic temperature 1 /T. Obtained regression lines were used to calculate oxygen activity at different temperatures, to calculate Gibbs free energy ΔG at the different temperatures and to calculate the single ΔG value for significant temperature of the graphite solidification. The results were processed by a statistical analysis of data files for the different types of graphite with flake, vermicular and spheroidal graphite. Each material has its proper typical oxygen activities range and individual temperature function of Gibbs free energy for analysing and governing casting quality.
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Abstract

High-chromium cast irons are used as abrasion resistant materials. Their wear resistance depends on quantity of carbides and the matrix supporting these carbides. The paper presents the results of cast irons of chemical composition (in wt. %) 19–22 Cr and 2–4.5 C alloyed by 1.7 Mo + 5 Ni + 2 Mn to improve their toughness, which were tested in working conditions of ferroalloys crushing. Tests showed that these as-cast chromium cast irons with mostly austenitic matrix achieved the hardness of 38-45 HRC, but their relative abrasion resistance Ψ ranged from 1.3 to 4.6, was higher comparing to the tool made from the X210Cr12 steel heat treated on hardness 61 HRC. The transformation of austenite into martensite occurs not only at the worn strained areas (on a surface of scratch) but also in their neighbourhood. Due to the work hardening of relatively large volumes of transformed austenite the cast iron possesses high abrasion resistance also on the surfaces where low pressures are acting. The tough abrasion-resistant cast iron well proved for production of dynamic and wear stressed castings e.g., crusher hammers, cutting tools for ceramic etc.
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Abstract

The modification is a widespread method of improving the strength properties of cast iron. The impact in terms of increasing amounts of eutectic grains has been thoroughly studied while the issue of the impact on the mechanical properties of primary austenite grains has not been studied in depth yet. The paper presents the study of both aspects. The methodology was to conduct the melting cast iron with flake graphite, then modifying the alloy by two sets of modifiers: the commercial modifier, and a mixture of iron powder with a commercial inoculant. The DAAS test was carried out to identify the primary austenite grains. The degree of supercooling was determined and the UTS test was performed as well. Additionally carried out the metallographic specimen allowing for counting grains. It can be concluded that the introduction of the iron powder significantly improved the number of austenite primary grains which resulted in an increase in tensile strength UTS.
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Abstract

The paper presents results of studies on the effect of the nodular cast iron metal matrix composition on the abrasive and adhesive wear resistance. Nodular cast iron with different metal matrix obtained in the rough state and ADI were tested. To research of abrasive and adhesive wear the pearlitic and bainitic cast iron with carbides and without this component were chosen. The influence of the carbides amount for cast iron wear resistance was examined. It was found, that the highest abrasive and adhesive wear resistance under conditions of dry friction has a nodular cast iron with carbides with upper and lower bainite. Carbides in bainitic and pearlitic cast iron significantly increase the wear resistance in these conditions. In terms of fluid friction the largest wear resistance had cast iron group with the highest hardness.
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Abstract

The results of research on stereological parameters of carbides in modified hypoeutectic chromium cast iron were shown in the paper. The effect of distance the casting heat centre of casting to the carbide phase morphology was examined. The samples for metallographic examination were taken from various locations of the model casting prepared in a special tester. This model casting was designed to simulate the solidification of heavy castings. Using the proposed methodology the relation of the distance from the model mould and the size, perimeter, length, width and the shape factor of carbides was examined. During the analysis, the values of stereological parameters of carbides changed on various sections of the model casting.
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Abstract

Silicon – molybdenum cast iron commonly called SiMo due to its unique properties has becoming more and more interesting engineering material. The history and development of this alloy is relatively long but, due to the significant difficulties during the manufacturing process resulting in the lower final quality than expected, it has not been applied to often in practice. The biggest challenge is its brittleness as a result of the carbides precipitations. During last few years, thanks to the many important researches made and the general foundry technology development, the interest in SiMo iron has been rapidly growing, especially for the castings for heavy duty applications like corrosion, high temperature and wear abrasion resistant parts. In the article the heat treatment attempts to improve the microstructure of SiMo castings has been presented. The goal was to destroy or at least to refine and uniformly distribute the carbides precipitations to improve mechanical properties of the exhaust manifold castings for the cars. The experiments were carried out for the alloy contains approx. 4% Si, 1% Mo and 3.2%C. The range of the research included: hardness measuring, standard mechanical properties and microstructure for as-cast state and after that the subsequent heat treatment process with another properties check. The result of the heat treatment was the elimination of pearlite from the metal matrix. Moreover, the changes of the carbide molybdenum – rich phase morphology were observed. The dispersion of the carbides precipitations in the carbides area was observed. The experiments proved the possibility to control the microstructure and the mechanical properties of the SiMo castings by means of heat treatment but only to some extent.
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Abstract

The article presents the results of the research on the influence of the shape of reaction chamber on spheroidisation of cast iron produced with use of the inmold method. The amounts of nodular graphite precipitates in castings produced with the use of different reaction chambers have been compared.
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Abstract

The resistance of cast iron to abrasive wear depends on the metal abrasive hardness ratio. For example, hardness of the structural constituents of the cast iron metal matrix is lower than the hardness of ordinary silica sand. Also cementite, the basic component of unalloyed white cast iron, has hardness lower than the hardness of silica. Some resistance to the abrasive effect of the aforementioned silica sand can provide the chromium white cast iron containing in its structure a large amount of (Cr, Fe)7C3 carbides characterised by hardness higher than the hardness of the silica sand in question. In the present study, it has been anticipated that the white cast iron structure will be changed by changing the type of metal matrix and the type of carbides present in this matrix, which will greatly expand the application area of castings under the harsh operating conditions of abrasive wear. Moreover, the study compares the results of abrasive wear resistance tests performed on the examined types of cast iron. Tests of abrasive wear resistance were carried out on a Miller machine. Samples of standard dimensions were exposed to abrasion in a double to-and-fro movement, sliding against the bottom of a trough filled with an aqueous abrasive mixture containing SiC + distilled water. The obtained results of changes in the sample weight were approximated with a power curve and shown further in the study.
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Abstract

The article describes the trend towards increased use of induction crucible furnaces for cast iron smelting. The use of gas cupola’s duplex process – induction crucible furnace – has been proved the effective direction of scientific and technical advance in the foundry industry. Gas cupolas and induction furnaces are used for cast iron smelting at the Penza Compressor Plant where in the 1960s the author developed and introduced gas cupolas for the first time in the world. In the article, the author represents the findings of the investigation on thermodynamics of crucible reduction of silicon, which is pivotal when choosing the technological mode for cast iron smelting in induction furnaces. The author proposes a new reaction crucible diagram with due account of both partial pressure and activity of the components involved into the process. For the first time ever, the electrochemical mechanism of a crucible reaction has been studied and the correctness of the proposed diagram has been confirmed.
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Abstract

The aim of the paper was an attempt at applying the time-series analysis to the control of the melting process of grey cast iron in production conditions. The production data were collected in one of Polish foundries in the form of spectrometer printouts. The quality of the alloy was controlled by its chemical composition in about 0.5 hour time intervals. The procedure of preparation of the industrial data is presented, including OCR-based method of transformation to the electronic numerical format as well as generation of records related to particular weekdays. The computations for time-series analysis were made using the author’s own software having a wide range of capabilities, including detection of important periodicity in data as well as regression modeling of the residual data, i.e. the values obtained after subtraction of general trend, trend of variability amplitude and the periodical component. The most interesting results of the analysis include: significant 2-measurements periodicity of percentages of all components, significance 7-day periodicity of silicon content measured at the end of a day and the relatively good prediction accuracy obtained without modeling of residual data for various types of expected values. Some practical conclusions have been formulated, related to possible improvements in the melting process control procedures as well as more general tips concerning applications of time-series analysis in foundry production.
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Abstract

In the dumps of metallurgical enterprises of Kazakhstan about 700 million tons of waste products are generated annually, and are polluting the atmosphere and the soil. The concentration of valuable components in waste products are no lower than in natural resources. The reserves of coal in the Ekibastuz basin are estimated to be more than a billion tons, and almost half of this is made up of ash. Every year, up to 30 million tons of ash-cinder waste is generated, which presents a serious threat to nature. Gallium and germanium concentrations in dumps are approximately 200 grams per ton, which is comparable to the content in coal before processing. The current research aims at creating a unit to obtain hydrogen-enriched water gas from Ekibastuz coal, with the production of zinc, gallium and germanium sublimates, copper-containing cast iron, slag wool and cast stone, through the joint processing of zinc-rich slag and ash-cinder wastes from thermal power plants. To achieve this, we used previous methods of extreme energy saving and a new method, the smelt layer with inversion phase. Experimental results from the “reactor inversion phase – rotary kiln” (RIPh) unit, which processed zinc-germanium contained slag, showed the potential to extract germanium from zinc sublimates, to reduce iron to the form of cupreous cast iron, and to obtain combustible gases and smelt suitable for slag-wool production. Calculations performed on the joint processing of Ekibastuz coal and zinc-rich slag using the proposed unit “reactor of inversion phase – rotary kiln – gas generator” showed it can obtain hydrogen-enriched water gas, along with the extraction of valuable components of primary raw material.
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